High voltage power transmission lines carrying voltages in the hundreds of kilowatt range have been constructed to extend from spaced towers or poles in terrain which is often practically inaccessible to land vehicles. In recent years, a number of methods and devices have been developed to facilitate the repair and maintenance of high voltage power transmission lines which are accessed by helicopter.
Lattice-type towers are employed for supporting multiple high voltage electrical conductors. The conductors are typically supported under the arms or bridges of such towers using a pair of suspension insulators per conductor. Periodically, it is necessary to replace the insulators because they are visibly damaged or as part of a general maintenance plan. Typically, insulators are attached via pins to the towers and via pins to a yoke plate which supports the conductor. These pins must be manually removed by linemen placed on the tower via helicopter in order to replace the insulators. Damaged or worn insulators are removed from the tower via helicopter and replacement insulators are delivered to the tower via helicopter. It will be appreciated that high voltage electrical conductors are extremely heavy and their great weight hanging from the end of an insulator makes it impossible to unpin and remove the insulator without first creating slack in the insulator. To accomplish this the conductor must be supported in some fashion during insulator removal and replacement. In the past, lineman have improvised temporary rigging to support the conductors. For example, multiple chain hoists have been used which are supported via multiple nylon slings at multiple spaced locations along tower girders. Such improvisation requires large amounts of equipment, is time consuming and fails to adequately distribute the weight of a supported conductor over a large area of the tower structure.
Accordingly, there exists a need for a device which may be safely emplaced on a tower via helicopter, which is light enough to be handled by a lineman on a tower, which is strong enough to support a heavy electrical conductor, which will be stable on a structure such as a lattice-type tower and which will distribute the weight of a supported conductor over the tower structure.